Sealing device for internal gear pumps



Aug. `21, 1945. J. B. PARSONS SEALING DEVICE FOR INTERNAL GEAR PUMPSFiled Opt. 7, 1943 @www SP1/UW dhnfjxrwnd, @M M f) Patented Aug. 21,19475 SEALING DEVICE FOR INTERNAL GEAR PUMPS l John B. Parsons, Toledo,Ohio Application October 7, 1943, Serial No. 505,304

1 Claim.

This invention relates to internal gear pumps but more particularly tothe sealing of the ends of such pumps.

It is necessary that opposite ends of internal gear pumps besatisfactorily sealed in order to militate against the loss ordissipation of pressure tain an effective seal. This is laborious andcostly,

thereby substantially increasing the cost of the assembly.

An object is to overcome the above dilculties and to produce a new andimproved seal which is entirely automatic in operation, and reliableunder all conditions, liquid or fluid pressure generated by the pumpbeing employed for this purpose, thereby substantially reducing the costof manufacture and assembly.

For purposes of illustration but not of limitation, an embodiment of theinvention is shown on the accompanying drawing in which p Figure 1 is aside elevation with parts broken away, of an electric motor driveninternal gear pumping unit;

Figure 2 is a transverse sectional view on the line 2--2 of Figure 1;

Figure 3 is a plan View of the ported plate which abuts against one endof the internal gear pump;

Figure 4 is a plan view of a plate which abuts against the lower end ofthe internal gear pump; and l Figure 5 is a spring washer or spacer fornormally holding the pump and plate parts in position.

The illustrated embodiment of the invention comprises a pumping unithaving a central block I on the upper side of which is suitably mountedan electric motor II and attached to the under side of the block Il) isa cup I2 which serves as a liquid reservoir. The cup I2 is held inposition by a bail pivotally mounted in any suitable manner on the blockI0. The electric motor II has an armature shaft I4 which projectsdownwardly into a pump housing I5 the lower end of which is open. Aclosure cap I6 is secured to the lower end of the pump housing I and issecured in place by screws Il. A packing ring I8 in the pumping housingprevents the escape of liquid along the closure cap I6.

A tube I8 depends into the reservoir I2 and terminates near the lowerend thereof, liquid being pumped through this tube to atransversepassage I9 which terminates in the downwardly extending port 20 openinginto the pump housing I5. In this manner it will be seen that the tubeI8, passage I9 and port 20 provide the inlet to the pump housing I5.Liquid is forced from the pump housing I5 through an upwardly extendingport 2I to a transverse passage 22 and thence laterally through apassage 23 to a suitable outlet nipple (not shown). A spring tensionedvalve 24 is slidable in the transverse passage 23. In the event thepressure exceeds a predetermined maximum, the valve 24 will be retractedsufficiently to enable the liquid to return to the reservoir I2 througha passage 25 which communicates with a vertical tube 2l similar to thetube I8. A port 26 enables liquid to be returned to the reservoir whichmay be in rear of the valve 2l. Reference is hereby made to myco-pending application Serial No. 452,865, entitled Motor pump unit, formore detail Idescription of the above described structure.

Arranged within the pump housing I5 is an internal gear pump P which maybe of any suitable or desired construction. In this instance, the pump Phas an outer rotor 28 formed with five notches .29, the side walls ofwhich are flaring along curvilinear surfaces 30. The inner rotor 3| isformed with four teeth, lthe side Walls of which are curvilinear .tocorrespond approximately with the curvilinear surfaces 3U of the outerrotor. The arrangement. is such that for each revolution of the innerrotor, the outer rotor is revolved four-iifths of a revolution. Theconstruction and operation of the pump P is wellknown to those skilledin this art and since the same forms no part of the present invention,iur-ther detail description is not considered necessary. Such pump isthe well-known structure commercially known as the Gerotor pump. It willbe noted that -the toothed ro'tor 3| is fixed for rotation to the endportion of the armature shaft I4 by a key 32 but is free for axialmovement along the shaft. Upon energizing the electric motor II, theinternal gear pump P is operated to draw liquid from the reservoir I2through the inlet passages above described and discharge the same underpressure through the outlet passages above described.

It will be manifest that in order for the pump to operate efficiently,leakage of iiuid must be prevented from the high pressure side of thepump to the low pressure side. It ls a desideratum that such seal beeffected in a simple and inexpensive manner so that not only will aneffective seal be established, but also that the wear on the parts sofar as the seal is concerned, be substantially reduced or entirelyeliminated. It will be understood that in the operation of the pump,both the gear parts 28 and 3| rotate so that the pump part 28 must havea nice fit within the nular groove 31 is formed on the housing on theupper side of and adjacent the periphery of the plate.

The pump housing I5 is of such size that a space is provided between thelower ends of the pump rotors 28 and 3l andthe closure cap I6. Arrangedwithin this space and abutting against the lower ends of the pump rotorsis a disclike plate 39, the peripheral portion of which engages thewalls of the housing. The plate 39 is preferably of metal, is relativelythin and exible and is formed with a central aperture 40 which issubstantially in alignment with the motor shaft I4. It will be manifestthat the inner rotor 3| is slidable along the armature shaft I4 and theouter rotor 28 is likewise slidable in the housing. In order to sustainthe weight of the rotors and the plate 39 and hold these parts in thedesired position when the pump is at rest, a spring washer isarrangedwithin the cavity or space 38 and is formed with` a plurality of radialspring arms 43 which bear against the under side of the plate 39. Thewasher 4I has a centrally arranged concave portion which bears againstthe central portion of the closure cap I6. It should be understood,however, that the spring pressure exerted by the washer 4I is notsufficient to establish the desired seal.

In operation, it Will be manifest that pressure uid passing Abetween theperiphery of the disc 39 and the walls of the housing will ll the space38 and impose an upward or axial pressure against the plate 39 andaccordingly the pump rotors. The pressure imparted by the fluid in thevspace 38 will of course be dependent upon the pressure generated by thepump. It is desired that the plate 39 be relatively thin in order thatit conform to the end surfaces of the rotors particularly in the eventof any unevenness or irregularities in these surfaces so that thepressure exerted by the fluid, liquid in this case, may slightly deformthe plate 39, thereby causing it to conform to the contour of thesesurfaces. The fluid pressure thus exerted will hold the plate 39 snuglyand in` sealing contact with the pump rotors 28 and 3I and owing to thegreater exposed area on the under side of the plate 39 as compared tothe internal area of the pump p arts containing the pressure uid, theplate 39 is held in sufficiently tight contact to produce the desiredsealing action, thereby militating against pump housing I5. At the upperend of the pump leakage of the pressure fluid from the high presbothsides of the plate. Otherwise inward deformation of the plate in thisregion would take place due to the high pressure imposed on the underside of the plate. In the event that the plate 39 were of greaterthickness and rigidity, such an aperture would not be necessary, butwhere the plate 39 is of relatively thin material, such aperture isdesirable.

As above mentioned, the annular groove 31 which is formed in the pumphousing I5 above the ported plate 33 relieves a portion of the upwardthrust or pressure which is created in the space or cavity 38. Thisvreduces the friction in that region and contributes to the efiiciencyof the assembly. In this connection it will be apparent that pressurefluid finds its way between the pump and the ported plate 33 and entersthe annular groove 31. In this manner a downward pressure on the upperside of the peripheral portion of the plate 33 is established sufficientto relieve a portion of the upward pressure created at the opposite endof the pump.

From the above description it will be apparent that I have provided anexceedingly simplebut effective seal foran internal gear pump wherebythe high and low pressure sides of the pump are satisfactorily sealedfrom each other,`-` the seal being effected by the pressure generated bythe pump. Thus the plates are forced against the ends of the pump withsufficient pressure to effect the seal but not to such an extent as tointerfere with the proper operation of the pump or to effect excessivewear on the pump parts.

It is to be understood that numerous changes in details of construction,arrangement and operation may be effected without departing from thespirit of the invention especially as defined in the appended claim.

What I claim is:

Pump sealing means comprising in combination, a housing having acylindrical cavity provided at one end with inlet and outlet passages,mating toothed pump rotor members arranged one within the otherl theouter rotor having an annular periphery providing a rotating t with `thewalls of said cavity, shaft means projecting into one end of saidhousing and secured at its i inner end'portion to the inner of saidrotor members for driving said rotors in eccentric relation to eachother for creating expanding and contracting chambers thereby to forcefluid under pressure from the inlet to the outlet passage, said rotormembers being spaced slightly from the opposlte end of said cavity toprovide 'a pressure space, a flexible plate of sheet material disposedin said pressure space and abutting against the adjacent surface ofboth' rotors, pressure uid being adapted to pass between said plate androtors and about the edges of said plate to said pressure space saidplate having an imperforate region covering such area of the rotorscreating said expand-ing and contracting chambers, said plate beingsufficiently thin to enable the fluid pressure withinv said pressurespace to cause the same to effect a` sealing relation with the end facesof the rotors adjacent thereto, said plate being of such shape anddimensions relative to the side walls of said cavity as to maintain saidregion in position to cover said area, and meansl for normally holdingsaid plate in abutment withy said pump rotor members.

JOI-IN B.'PARSONS.

